Boron nitride is a synthetic material made from boric acid or boron trioxide. Among its various crystalline forms, its hexagonal allotrope, hexagonal boron nitride (h-BN), can be similar to graphite in structure and layered form but with alternating B and N atoms. h-BN has beneficial thermodynamic (air stable up to 1,000° C.) and chemical stability, exceptional hardness, and great thermal conductivity while being electrically insulating. These properties make hBN suitable for many technological applications. hBN can also exhibit features such as high thermal conductivity and mechanical strength, along with chemical stability. The hydrophobic nature of hBN can be useful in non-wetting surfaces or underwater constructions. hBN can also be used for corrosion-resistant surfaces. Current commercial products of hBN include various thermal management materials such as thermal pads, thermal grease, thermal coatings, and various cosmetics (because of their role as solid lubricants). Furthermore, high neutron absorption cross-section of boron and advantages of multilayered nanostructured materials (i.e., numerous interfaces) to sink radiation, make h-BN a suitable candidate for intercalation in ceramics for nuclear shielding.
Porous cement composites including hBN are described in Hexagonal Boron Nitride and Graphite Oxide Reinforced (Advanced Functional Materials, Vol. 25, Issue 45, Pages 5621-5630). This reference describes cement and concrete composites utilizing non-functionalized, non-exfoliated hBN and graphite oxide.
We describe herein a class of multifunctional hexagonal Boron Nitride (hBN)-cement composites utilizing treated, functionalized, and/or exfoliated hBN. Embodiments described herein relate to synthesis, exfoliation, functionalization, hydrolysis, agitating, sonicating, mixing and/or intercalation processes used to develop composites comprising treated hBN that exhibit enhanced properties. In some embodiments, these properties include, but are not limited to strength, toughness, stiffness, ductility, thermal resistance, radiation-resistance, rheology, viscosity, low permeability, durability, and/or acid resistance. In some embodiments, the material may be a protective coating. Enhanced properties may also include compatibility with a wide variety of functional groups, including, but not limited to hydroxyl, amine, and/or thiol groups. In certain embodiments, the disclosed composites include a variety of cementitious materials including but not limited to Portland cement, well cement, calcium aluminate cement, polymers, and/or other binders. In some embodiments, because of the unique properties of treated hexagonal boron nitride, the final composite is resistant to degradation at much higher temperatures than typical cementitious materials and other similar hybrid composites.
Other embodiments disclosed herein relate to construction, transportation, well cementing (both primary and remedial cementing), drilling fluids, nuclear industry applications, radiation rich environments such as outer space, aerospace or medical applications, 3D printing of composites, refractory materials, lubrication, scaffolds for high-temperature combustion sensors, removal of harmful oxyanions such as arsenate, chromate, phosphate from contaminated water and other applications of the disclosed composites.
Certain embodiments relate to composites, mixtures and/or crystal structures comprising hBN, calcium-silicate-hydrate, tobermorite, and/or other products involved in the hydration of cement. These embodiments may further be combined with cement, and/or concrete materials and/or other composites.
In some embodiments, synthesis methods include, but are not limited to solid state reactions and/or solution-based processing of hBN sheets, ribbons, tubes, and/or particles. These methods may be performed at high temperature or at room temperature. The synthesis of treated, exfoliated, hydrolyzed, and/or functionalized boron nitride sheets, ribbons, tubes, and/or particles may be performed first with or without post processing, filtering and/or additional chemical reactions. In some embodiments, the hBN material may then be incorporated into cement or cementitious material, leading to the creation of a new composite material. The functionalization may include, but is not limited to, a variety of functional groups such as hydroxyl, carboxylates, carbonyls, amines, etc. The composite may take advantage of several properties of hBN such as high thermal conductivity and/or thermal stability, low thermal expansion coefficient, high chemical stability, lubricity, radiation tolerance and/or acid tolerance to provide a class of hybrid materials that offers enhanced properties including but not limited to structural and rheological properties and resistance to extreme conditions. In some embodiments, our composite will (1) allow for construction of high-strength, and/or more durable hybrid cement/concrete structures that offer enhanced material properties than conventional cement/concrete, including (but not limited to) applications for construction, well cement (including but not limited to class G and H well cement as well as primary and remedial cementing) and cement used in concrete of nuclear power plants, and/or transportation infrastructure, (2) provide a material that can be used for both general infrastructure and high-temperature applications simultaneously, thus eliminating the need for separate materials, and (3) reduce overall costs by lower replacement expenses (increased durability) and excess material expenses due to (1) and (2).